Question: What is the cation with the lowest isospin z-component whose instance of is cation ?
Paraphrase: Which cation has the lowest isospin z-component whose instance of is cation?
SPARQL (Wikidata): select ?ent where { ?ent wdt:P31 wd:Q326277 . ?ent wdt:P1127 ?obj . ?ent wdt:P31 wd:Q326277} ORDER BY ASC(?obj)LIMIT 5 
Answer: triton, deuteron